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electrical:inverter [2023/04/09 18:24]
frater_secessus [Sizing your inverter] |
electrical:inverter [2024/04/20 22:18] (current)
frater_secessus [efficiency] |
| It is **more efficient to use DC power directly** whenever possible. In particular it is more efficient than running a laptop of phone charger off an inverter.((http://www.cheaprvliving.com/forums/Thread-Here-s-one-for-you-inverter-lovers)) | It is **more efficient to use DC power directly** whenever possible. In particular it is more efficient than running a laptop of phone charger off an inverter.((http://www.cheaprvliving.com/forums/Thread-Here-s-one-for-you-inverter-lovers)) |
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| AC-only items will require an inverter. [[electrical:12v:wallwart|Devices that run off a "wall wart" adapter]] almost never require an inverter. | Note: **only AC loads will require an inverter**. [[electrical:12v:wallwart|Devices that run off a "wall wart" adapter]] that output DC almost never require an inverter. Things that charge off USB (phones, fans, tablets, etc) can use a [[https://amzn.to/3JmopvO|12v-to-USB port]]. Laptops often have car chargers that run off 12v ([[https://amzn.to/3Wax1Nw|example]]). Search for "[specific make/model] car charger" |
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| | ===== efficiency ===== |
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| | Inverting from DC to your local shore power spec will necessarily incur losses. These might be 10-30%, depending on the inverter, the inverter's efficiency spec, etc. In the absence of hard information you might use 20% losses as a rule of thumb. This means it will require 20% more power to run your load than the rating spec. |
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| | 50w / 0.8 efficiency = 60w demanded from the system |
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| * In [[https://www.youtube.com/watch?v=wimTJw_Gpgk|an apples-to-apples comparison]] knurlgnar24 found a microwave to run 10% less efficiently and at 20% less power on MSW. | * In [[https://www.youtube.com/watch?v=wimTJw_Gpgk|an apples-to-apples comparison]] knurlgnar24 found a microwave to run 10% less efficiently and at 20% less power on MSW. |
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| | Also see [[https://www.reddit.com/r/diySolar/comments/yyd20a/pure_sine_wave_inverters_what_is_real_and_what_is/ix136m7/|this technical post]] on the topic by therealtimewarren. |
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| ===== Pure Sine Wave ===== | ===== Pure Sine Wave ===== |
| Not all PSW are prohibitively expensive. Bestek makes [[https://amzn.to/3N4YE3S|a 300w PSW for about $50]]. See [[https://www.amazon.com/gp/customer-reviews/R3UKQ7A0GQ196N/ref=cm_cr_dp_d_rvw_ttl?ie=UTF8&ASIN=B07KQ4Q2L5|the top-rated review]] for oscilloscope testing and limitations. | Not all PSW are prohibitively expensive. Bestek makes [[https://amzn.to/3N4YE3S|a 300w PSW for about $50]]. See [[https://www.amazon.com/gp/customer-reviews/R3UKQ7A0GQ196N/ref=cm_cr_dp_d_rvw_ttl?ie=UTF8&ASIN=B07KQ4Q2L5|the top-rated review]] for oscilloscope testing and limitations. |
| ===== inverter chargers ===== | ===== inverter chargers ===== |
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| {{ https://m.media-amazon.com/images/I/61wb7PGYPNL._AC_UL320_.jpg?150}} \\ | {{ https://m.media-amazon.com/images/I/61wb7PGYPNL._AC_UL320_.jpg?150}} \\ |
| An //inverter charger// performs several functions: | |
| | //Inverter/chargers// are most often found on rigs that are on shore power much of the time and run heavy AC loads |
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| | It provides several functions: |
| - invert 12v battery power to 120vac | - invert 12v battery power to 120vac |
| - pass-through shore power when available | - pass-through shore power when available, with auto-switching |
| - some can bond shore and battery power to support heavy 120vac loads | - some can bond shore and battery power to support heavy 120vac loads |
| - charge battery banks like a [[electrical:converter|converter]] | - charge battery banks like a [[electrical:converter|converter]] |
| | - some also handle solar charging |
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| They tend to be [[https://amzn.to/2KMcImw|expensive]], some over $1000. | They tend to be [[https://amzn.to/2KMcImw|expensive]], some over $1000. |
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| | Note: the Victron Multiplus line has outputs for maintaining the starter battery: |
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| | >> The main DC terminal can supply the full output current. The second output, intended for charging starter battery, is limited to 4A and has a slightly lower output voltage.((https://www.victronenergy.com/upload/documents/Manual-MultiPlus-3k-120V-(firmware-xxxx4xx)-EN.pdf)) |
| ===== Sizing your inverter ===== | ===== Sizing your inverter ===== |
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| Once you have made your MSW vs. PSW decision the next step is **sizing the inverter** (picking the right capacity). | Once you have made your MSW vs. PSW decision the next step is **sizing the inverter** (picking the right capacity). |
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| | ==== special case: tiny loads ==== |
| | [[https://amzn.to/43RbueW|{{ https://m.media-amazon.com/images/I/81-P5bKVCzL._AC_UL320_.jpg?125}}]] |
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| | For ~120w loads you can use [[https://amzn.to/4cMWwdW|a small inverter]] intended to be powered by the [[electrical:12v:ports#the_cigarette_outlet|cigarette lighter port]]. The ports are typically fused at 10A, hence the ~120w wattage limit (12v x 10A = 120w).((technically you could use any size inverter as long as you remembered not to draw >10A)) |
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| | Note: Ciggy ports are already prone to failure and poor connections. An inverter that hangs out of the socket will make matters worse. To avoid stressing the socket you can use an inverter with a built in power cord (as pictured above). If you already own [[https://amzn.to/4aLoUuT|one designed to live in the socket]]((don't buy this!)) consider using [[https://amzn.to/3UgnTWF|a soft wire extension]] that will allow you to relocate the inverter. |
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| | In any case, find out what kind of fuse your ciggy port uses and have some on hand. Mistakes are easy to make and easy to fix (if you have the spare fuse waiting). |
| ==== estimating your needs ==== | ==== estimating your needs ==== |
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| You will need to know the largest draws you will need to meet **at the same time**. If your TV is 40w, and your your laptop is 100w you would need (40w + 100w) * 1.10((inverter losses)), or an inverter that can power at least **154w**. | You will need to know the largest draws you will need to meet **at the same time**. If your TV is 40w, and your your laptop is 100w you would need (40w + 100w) * 1.10((inverter losses)), or an inverter that can power at least **154w**. |
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| Note that motorized equipment like drills likely have **greater current requirements for startup and for running**. Be sure to measure both startup and running (see below). There are tricks you can use to minimize the start load, like starting a sewing machine at a low-load position((http://www.cheaprvliving.com/forums/Thread-Is-it-possible-to-Boondock-with-an-electric-sewing-machine?pid=165956#pid165956)), or //easing// into the trigger of a variable-speed power tool. | Motorized equipment like drills likely have **greater current requirements for startup and for running**. Be sure to measure both startup and running (see below). There are tricks you can use to minimize the start load, like starting a sewing machine at a low-load position((http://www.cheaprvliving.com/forums/Thread-Is-it-possible-to-Boondock-with-an-electric-sewing-machine?pid=165956#pid165956)), or //easing// into the trigger of a variable-speed power tool. |
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| | Note that to **actually power the inverter** without voltage sag or dipping so much into battery capacity you may want need something like a 1:1 ratio of panel:inverter on flooded lead and 1:2 on AGM or lithium.((https://www.solarpaneltalk.com/forum/off-grid-solar/solar-living/15554-how-to-increase-solar-panel-output-amps?p=181738#post181738)) This would mean 400w of solar to run a 400w inverter (dipping into the battery as needed) or 400w of solar for 800w of inverter on AGM/Lithium, which have greater throughput. |
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| The low voltage cutoff is to protect your batteries from [[electrical:depth of discharge|over-discharge]]. The high voltage cutoff is to protect the inverter itself. In addition, [[https://forum.solar-electric.com/discussion/comment/419096#Comment_419096|the current consumed by the inverter may increase]] as bank voltage drops. | The low voltage cutoff is to protect your batteries from [[electrical:depth of discharge|over-discharge]]. The high voltage cutoff is to protect the inverter itself. In addition, [[https://forum.solar-electric.com/discussion/comment/419096#Comment_419096|the current consumed by the inverter may increase]] as bank voltage drops. |
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| HandyBob((https://handybobsolar.wordpress.com/)) reminds us that //"Properly adjusted solar systems with temperature compensation will regularly exceed the 15 volts many inverters use as a high voltage shut down."//((https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/)) | HandyBob((https://handybobsolar.wordpress.com/)) reminds us that //"Properly adjusted solar systems with temperature compensation [for lead batts] will regularly exceed the 15 volts many inverters use as a high voltage shut down."//((https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/)) |
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| | ===== cooling ===== |
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| | Most inverters have fans to pull cooler air through them. Some do this only when they are too warm, or at a given power output regardless of temp, and some run 100% of the time. |
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| | If your fan runs only when hot, do not turn off the inverter until the fan has cooled the insides and stopped running. With continuous running fans put your hand on the inverter after the load is stopped to feel when it is safe to power off the inverter. |
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| | ===== running big loads at lower power ===== |
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| | see [[electrical:triac|this experimental article]] |
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| ===== sharing power ===== | ===== sharing power ===== |
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| Because higher voltage power has less losses over long wires, it may be most efficient to share power between RVs as 120v. The donor vehicle would invert to 120v, plug in an extension cord to their inverter and run it to the recipient. The recipient could plug it cord into their [[electrical:shore_power|shore power]] inlet or use it as 120v. | Because higher voltage power has less losses over long wires, it may be most efficient to share power between RVs as 120v. The donor vehicle would invert to 120v, plug in an extension cord((outdoor rated and approprate gauge)) to their inverter and run it to the recipient. The recipient could plug it cord into their [[electrical:shore_power|shore power]] inlet or use the end of the extension cord directly. |
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| ===== differences from shore power 120vac ===== | ===== differences from shore power 120vac ===== |
